Using a medical application as an example, a primary medical device is positioned, and inserted into a location within a subject. When introducing a primary medical device into a patient, one type of procedure utilizes an assembly of additional devices that interact with the primary medical device to aid in precision introduction of the primary medical device.
An example of a primary medical device includes an elongated structure, such as a catheter, designed to function with one end inside the patient, and operational control external to the patient. The primary medical device includes an active portion attached to a distal end that may include, but is not limited to: a biopsy probe; drug delivery capability; a tissue removal instrument such as a laser; an instrument for placing an electrode; etc.
One type of a secondary medical device includes an introducer, that may be used in a surgical procedure to move a primary medical device along an introduction axis, into or out of the patient. Secondary medical devices may also include a trajectory guide, or alignment device that positions the introducer in the direction of the area to be explored in the patient.
It is often desirable in precision surgical procedures such as neurosurgery that the exact position of the primary medical device is known in relation to the body of the patient. The relative position of the primary medical device is carefully controlled by secondary medical devices such as introducers and alignment devices. In one example, the alignment device fixes the introduction axis in three-dimensional space relative to the patient, and the introducer controls the position (depth inside the patient) of the primary medical device along the introduction axis.
To ensure that the secondary medical devices are accurately adjusted relative to the location of interest inside the patient, the alignment device is typically fixed relative to a patient reference frame. The patient reference frame includes the actual patient, and other objects or devices that the patient is fixed in relation to. The alignment device may therefore be fixed directly to the patient in one embodiment. Alternatively, the alignment device may be fixed to an intermediate object such as a stereotactic headframe or similar object attached to an operating table, with the patient being fixed to the operating table.
During positioning of an alignment device, an introduction axis is free to move in at least one degree of freedom, however after positioning is complete, it is desirable to have the introduction axis of the alignment device fixed in space. However, actuation of fixing devices typically causes an unwanted shift in the orientation of the introduction axis of the alignment device.
What is needed is a device and method to fix a desired position of an introduction axis of an alignment device with improved accuracy that reduces such unwanted shifting.